JP 2008-228419A proposes one exemplary control system, which performs model estimation (prediction) control. The control system estimates a current flowing to a three-phase motor in correspondence to each switching mode determined by on/off of switching devices of an inverter (power conversion circuit), and operates the inverter in a switching mode, which minimizes an error between the estimated current and a command current. Since the inverter is operated to optimize changes of the current estimated based on an output voltage of the inverter, the follow-up characteristic of an actual current relative to the command current at the time of transient condition is improved relative to a case of PWM control performed by triangular wave comparison.
The model estimation control is therefore highly effective for a control system for a motor/generator as a main in-vehicle apparatus, which requires high performance in the transient-time follow-up characteristic.
In case the model estimation control is used, it is possible to change the switching mode to an optimum mode each time the switching mode is allowed to be updated. As a result, it is likely that the switching mode will be changed too frequently.